1. Field of the Invention
The present invention relates to an inkjet printer provided with an ink circulation route, and particularly, to an inkjet printer adapted to supply ink from an ink tank to an inkjet head through an ink circulation route, with pressures corresponding to differences in water head of liquid level in between.
2. Description of Related Arts
There has been wide use of inkjet printers adapted to propel droplets of ink from an inkjet head onto a print sheet, to form images thereon. Among such inkjet printers, there have been those including an ink tank disposed in position higher than the inkjet head, and adapted to work in a state air-communicating with the atmosphere, to supply ink from the ink tank to the inkjet head.
There is an inkjet printer disclosed in Japanese Patent Application Laying-Open Publication No. 2001-219580, with configuration to supply ink to nozzles of an inkjet head with pressures corresponding to differences in water head relative to a liquid level of an ink tank, affording to control the liquid level of ink tank to supply stable pressures of ink to the nozzles. There is a flow of ink supplied to the inkjet head, having an excess of ink collected, and returned through a pump to the ink tank. The inkjet printer thus has an ink supply line of a circulation type configured to circulate ink from the ink tank, through the inkjet head, again to the ink tank.
By the way, for use in inkjet printers, available types of ink have tendencies to get the lower in temperature the higher in viscosity, as their properties. High viscosities of ink disable propelling ink droplets through nozzles at adequate discharge speeds. To this point, there is an inkjet printer with ink circulation route disclosed in Japanese Patent Application Laying-Open Publication No. 2008-37020, with configuration to work when the ink temperature is low, to heat ink to enable propelling ink droplets through nozzles at adequate discharge speeds.